Stability of the Gyroid Phase in Diblock Copolymers
at Strong Segregation

E.W. Cochran, C.J. García-Cervera, and G.H. Fredrickson.

Abstract

We report high resolution self-consistent field theory (SCFT)
calculations that show the gyroid phase, Q230, to be stable in
conformationally symmetric linear diblock copolymer melts prepared
within the strong segregation regime, \chi N = 100, over a
composition window of ~ 1.5%. This window broadens with the
introduction of conformational asymmetry. The SCFT equations were
solved using a novel pseudospectral approach with a plane wave
basis and periodic boundary conditions. Saddle point field
configurations were obtained using a semi-implicit Seidel
relaxation algorithm. The modified diffusion equation was solved
using a fourth-order backward differentiation formula and implicit
treatment of the Laplacian operator. Our calculations are
consistent with recent experimental observations of Q230 in
strongly segregated diblocks.